Let's 'frame' the house with a large tree in the background. Most people have a difficult time drawing realistic looking trees but, not to worry, we're not going to get very detailed with this one. When you a drawing trees, a good tip to remember is that a tree's structure is very similar to the structure of a leaf. The branches of a tree branch out from the trunk in the same manner as veins in a leaf branch out from the center. Go to your yard and get a leaf if it will help.
Let's create a new raster layer for this tree. Drag the layer button so that it is below the HOUSE layer so our tree will be behind the house.
Base colors:
Using a dark brown and a 1 pixel brush, roughly lay out the location of the trunk and some branches. This will only be a guide to give us a general shape for our tree ...so just make it a quick sketch that resembles the veins of a giant leaf (using dark brown). Refer to above image(a). Now use dark green to fill in some leaf area, leaving a lot of open space. Scribble in some dark green over the branches with a 3 or 4 pixel brush. Refer to above image (b). Next, scribble in some medium green over the dark green, leaving a lot of dark toward the center. Refer to above image (c). Add some very light green highlights over that.
Creating detail:
Using the 1 pixel brush, go back over your scribbles and break up some large areas of color with a contrasting color or erase some if you got the tree too dense. (Leave some holes for the birds to fly through.) Using dark or medium green, outline some small clumps. Refer to above image(d).
All of the branches you sketched in earlier are probably hidden now. Use some browns to paint a few branches back in where they can be seen between the leaves. Use dark brown in the open spaces (against the sky) and medium brown against the dark areas. Refer to above image(e).
Speed Tip: To quickly create detail around the edges of tree, draw a detailed leaf group off to one side using a few shades of green. Copy and past the leaf group a few times around the edges. Mirror it or flip it in a few places to get variety. Refer to above image(f).
Now we need to add some flowers to the front yard!